The present invention refers to equipment for ultrasonic testing of tubes or pipes and more particularly, the invention relates to a test stand for the ultrasonic testing and inspection of tubes or pipes in which pipes and tubes of different wall thickness-to-diameter values (T/D ratios) can be tested.
The testing of tubes or pipes as to flaws and defects, using ultrasonic beams and using further the immersion technique, i.e. using water as a coupler fluid for coupling the ultrasonic transducer to the pipes material, require a specific angle of incidence of the ultrasonic beam in relation to a normal on the tube or pipe surface, through the point of entrance of the beam into the wall of the tubes. Upon entering the tube's wall, the test beam undergoes refraction because the tube/fluid interface is also a discontinuity as far as the propagation of sonic and ultrasonic vibrations is concerned. The angle of refracted radiation beam to that normal will in the following be called the test angle of refraction, because it results from refraction of the incident test beam as it is being refracted via in the water-tube material interface. It was found that for each particular type of tube and pipe, as defined by a specific T/D ratio, and for a specific material (e.g. steel), there is but one such test angle of refraction for a useful test beam. However, depending upon the T/D ratio, the test angle of refraction varies greatly and may be as low as 33.degree., as high as almost 90.degree. C., this being true particularly if transversal waves are being employed.
In our co-pending application, Ser. No. 770,587, filed Feb. 22, 1977, now U.S. Pat. No. 4,058,000, we have proposed a method to vary the test angle of refraction through temperature control of the coupler fluid. The disclosure of that application is incorporated by reference in this application.